Steer-by-wire technology approaches production vehicles

Taking a page from the world of aviation, Nissan Motor Co. plans to
enter the "by-wire" world and control the steering of a future
Infiniti vehicle with electronic signals.

The decision to bring steer-by-wire to a production vehicle is a
major one for the automobile industry because it lays the
foundation for eventual elimination of the mechanical components
that now connect the driver to a vehicle's tires.

"There are a lot of advantages to this," Infiniti spokesman Kyle
Bazemore told Design News. "It enhances the driving experience.
And in the future, after consumer acceptance of the technology, we
could theoretically do away with the mechanicals and save the
weight."

The next-generation steering system, as Nissan calls it, works by
endowing the steering wheel with sensors that read the desired
steering angle. Data from the sensors is sent to one of three
electronic control units (ECUs), which activate electric motors on
the vehicle's steering rack. In contrast, conventional steering
uses a direct mechanical connection to the rack-and-pinion.

In truth, the new Nissan system won't eliminate the mechanical
connection to the driver. Instead, it will use the mechanical
connection as a redundant system, only in cases of extreme
emergency. If, for example, a power supply conks out or all of the
ECUs fail, it will employ a back-up clutch to mechanically connect
the steering wheel to the tires. "The clutch is disengaged 999,999
times out of a million," Bazemore told us. "But the steering shaft
is still there, just in case."

Nissan said steer-by-wire will enhance the driving experience.
When it reaches the market late next year, it will eliminate some
of the vibration from rough road surfaces and it will minutely
adjust tire angles to compensate for crosswinds and sloped
surfaces. At the same time, it will enable drivers to "feel" the
road. Grip information, such as slipperiness, will be transferred
back to a steering force actuator that will allow the steering
wheel to retain some of its original feel.

"Theoretically, you
could have no steering feel at all, but that would not be good for
drivers," Bazemore said. "That's why we dialed some -- but not all
-- of the steering feel back into the system."

I am sure the Nissan engineers have figured out the response characteristics of the wired steering systems vs. the mechanical one so the driver will notice little change when the backup / redundant system takes over. But the situation described by @Ian McMillan above does bring up an important issue. It would be nice to know more about this.
MP Divaar

I like the idea of compensating for cross-winds; but experience in the aircraft industry (which uses triple-redundancy) has shown that unless fly-by-wire has some means of being very quickly by-passed when the voting circuit makes a mistake, you can find yourself in real trouble real quick. Split-second timing can be vital, can be life-and-death... I still feel the butterflies there